Nabesite

Nabesite is a rare silicate mineral of the zeolite group with the chemical formula Na₂BeSi₄O₁₀·4(H₂O). It occurs as colorless to white orthorhombic crystals in thin platy mica like sheets. It has the zeolite structure. Its Mohs hardness is 5 to 6 and its specific gravity is 2.16. The reported refractive index values are n_α=1.499, n_β=1.507, and n_γ=1.511.

General
Category	Tectosilicate minerals, zeolite group
Formula	Na2BeSi4O10·4H2O
Strunz classification	8/J.0-
Dana classification	77.1.5.11
Crystal system	Orthorhombic
Crystal class	Disphenoidal
Space group	P212121 (No. 19)
Unit cell	a=9.748Å, b=10.133Å, c=12.954Å
Identification
Formula mass	391.84
Colour	Colourless, white
Crystal habit	Platy, thin/flat
Cleavage	Good
Fracture	Brittle, uneven
Mohs scale hardness	5-6
Luster	Vitreous
Streak	White
Diaphaneity	Transparent
Specific gravity	2.16
Density	2.16
Birefringence	0.012

It was discovered in the Ilimaussaq intrusive complex, of southwest Greenland, and first recognized in 2000. It occurs in tugtupite-bearing albitite, a rare highly alkaline igneous rock.

References

• Webmineral.com data
• Mindat.org

External links

• Structure type NAB